Numerous examples of articles for organizing, storing, protecting and displaying communications media, such as papers, audio and video cassettes, compact discs and the like, are known. Common examples include portfolios, folders, notebooks, loose-leaf binders, audio and video cassette cases and compact disc holders. Although different in many respects, these articles share a salient feature of manufacture. Namely, each of these articles may be manufactured using a casing board that includes a substrate consisting of a front cover, a rear cover and a spine positioned between and hingedly connected to the front cover and to the rear cover along opposed, laterally extending hinge lines. Accordingly, the article can be closed to organize, store, and protect the communications media, or can be opened to display the communications media.
The manufacture of such articles has changed little in recent years. The substrate is typically made of relatively thick, relatively rigid material, such as cardboard, fiberboard or corrugated paper, which is commonly referred to as "chipboard". The chipboard is positioned between an inner cover and an outer cover made of a thin sheet of plastic material, and the inner cover and the outer cover are joined together at their edges along the periphery of the chipboard. The most well known of these articles is perhaps the conventional loose-leaf binder. Typical loose-leaf binders are shown and described in U.S. Pat. No. 5,069,568 to Acker and U.S. Pat. No. 5,030,027 to Bachrach et al. The construction of a loose-leaf binder having a retainer mechanism and an exterior display pocket is disclosed in the Bachrach patent and in U.S. Pat. No. 2,801,115 to Federbush et al.
The loose-leaf binders disclosed in the Acker, Bachrach and Federbush patents are manufactured from a casing board including a substrate consisting of a front cover portion, a rear cover portion and a spine portion positioned between and hingedly connected to the front cover portion and the rear cover portion along opposed, laterally extending hinge lines. The front cover portion, rear cover portion and spine portion are separately formed and sandwiched between an inner cover and an outer cover. The inner cover and the outer cover may be made of a thin sheet of any fabric, paper or plastic material, but most commonly are made of a thermoplastic material, such as vinyl, that is readily joined at the edges of the inner and outer covers along the periphery of the substrate by electronic welding, such as ultrasonic or radio frequency (RF) welding.
Casing boards made of thin sheets of vinyl joined along laterally extending hinge lines and along the periphery of the substrate present certain disadvantages. Firstly, vinyl, and in particular polyvinylchloride (PVC), is an environmentally unfriendly material. Vinyl materials decompose slowly in landfills and leach toxins as they decompose. The same toxins are released when the vinyl materials are incinerated. Accordingly, there is increasing pressure from environmentalists to utilize environmentally friendly materials, for example polyolefins, such as polypropylene and polyethylene, in the manufacture of casing boards for portfolios, folders, notebooks, loose-leaf binders, audio and video cassette cases, compact disc holders and the like.
Another disadvantage presented by casing boards made of thin sheets of vinyl is that the edges of the inner cover and the outer cover must be joined by electronic welding techniques (i.e. ultrasonic or RF). Thin sheets of vinyl are not susceptible to thermal welding (also know as heat sealing or thermo-welding) because vinyl materials have a relatively low softening temperature. Thus, vinyl materials tend to liquify and adhere to the thermal welding dies before the edges of the inner cover and the outer cover plasticize and fuse. RF welding, which is the most common type of electronic welding used in the manufacture of casing boards for loose-leaf binders, requires the RF energy to be applied to both the inner cover and the outer cover simultaneously to form each weld seam. Thus, RF welding results in sharp edges along the periphery of the binder. Furthermore, because the RF energy cannot penetrate the thickness of the substrate, the front cover portion, the rear cover portion and the spine portion must be separately formed to permit the inner cover and the outer cover to be welded along the opposed, laterally extending hinge lines which join the front cover portion and the rear cover portion to the spine portion.
Another disadvantage is that thin sheets of vinyl are somewhat brittle, particularly when subjected to temperature extremes. Thus, the sharp edges along the periphery tend to cold-crack and split. When the edges of the binder split, the inner cover and the outer cover separate. Because vinyl materials do not adhere well to chipboard, the inner cover and the outer cover typically are not affixed to the interior and exterior surfaces, respectively, of the substrate. Once the edges separate, the inner cover and the outer cover of the binder are likely to rip or tear away from the substrate. The inability of vinyl materials to adhere well to chipboard also results in air being entrapped between the inner cover and the substrate, and between the outer cover and the substrate. In addition to the danger presented by the sharp edges of the casing board, the sharp edges and air pockets which result from the RF welding process diminish the aesthetic appearance of the finished article.
Using electronic welding techniques, and in particular RF welding, to produce articles such as loose-leaf binders also results in increased material and manufacturing costs. As previously mentioned, RF welding requires the front cover portion, the rear cover portion and the spine portion to be separately formed, thereby adding cutting and positioning steps to the process as well as the two additional welding steps needed to form the opposed, laterally extending hinge lines. Polyolefin materials, and in particular thin sheets of polypropylene, are lighter in weight and stronger than thin sheets of vinyl having the same thickness. Accordingly, the sheets of polypropylene used to manufacture casing boards may be thinner than required when sheets of vinyl are used. Furthermore, and perhaps most importantly, RF welding requires a dwell period to generate enough heat to plasticize and fuse vinyl materials. Thus, RF welding the periphery and hinge lines of casing boards made of vinyl materials is not a continuous process. In contrast, thermal welding casing boards made of polyolefin materials is a substantially continuous process. Accordingly, the manufacture of articles such as loose-leaf binders by thermal welding is faster and is suitable for fully automatic, high speed production.
A final disadvantage of casing boards made of thin sheets of vinyl is that the use of electronic welding, and in particular RF welding, diminishes the aesthetic appearance of the finished article. As previously mentioned, RF welding results in sharp edges and possibly air pockets being introduced during the manufacture of the article. Even if the air pockets are eliminated, for example by welding in a vacuum chamber or drawing a continuous vacuum on the casing board during the welding process, the inner and outer covers are not affixed to the substrate and thus may become wrinkled as the article ages. Finally, and of great importance to the wholesale purchaser, vinyl materials are not readily receptive to printed indicia. Although it is possible to print on vinyl, anything as sophisticated as four-color graphic printing, is cost prohibitive and is not durable enough to withstand ordinary use without fading, blurring or rubbing off. Accordingly, many such articles are provided with a clear overlay which defines an exterior pocket for receiving a merchandising insert having the desired indicia printed thereon.
Casing boards made of thin sheets of vinyl materials RF welded together along opposed, laterally extending hinge lines, however, necessarily result in the formation of three separate exterior pockets, one each adjacent the front cover portion, the rear cover portion and the spine portion. Accordingly vinyl RF welded casing boards require the use of separate merchandising inserts to display printed indicia across the full-width of the outside surface between the longitudinal edges of the casing board. For example, it is not possible to display a single-sheet merchandising insert on a loose-leaf binder make of thin sheets of vinyl that are joined together along the hinge lines and the periphery of the substrate by RF welding.
Some of the disadvantages of manufacturing a casing board wherein the edges of the inner and outer covers are electronically welded along the hinge lines and the periphery of the substrate have been addressed by utilizing polyolefin materials, and specifically thin sheets of polyethylene and polypropylene, in a process commonly referred to as "turned-edge construction". Thin sheets of polyolefin materials can be readily affixed to the chipboard substrate with an adhesive and can be readily affixed to other thin sheets of polyolefin materials by thermal contact welding. In turned-edge construction, the outer cover, known as the "outer wrap" of the binder, has longitudinal and lateral dimensions that are slightly greater than the longitudinal and lateral dimensions of the substrate.
The outer wrap is positioned adjacent the exterior surface of the substrate such that the longitudinal and lateral edges of the outer wrap extend beyond the periphery of the substrate. The longitudinal and lateral edges of the outer wrap are then turned over the periphery of the substrate and affixed, typically with an adhesive, to the interior surface of the substrate. The outer wrap may also be affixed to the exterior surface of the substrate with an adhesive to eliminate wrinkles and air pockets on the front cover portion, rear cover portion and spine portion. In some cases, a liner made of a thin sheet of polyolefin material is also affixed to the interior surface of the substrate so that the substrate is completely encased by the outer wrap and the liner.
Previous attempts to provide turned-edge casing boards made of thin sheets of polyolefin materials including a clear overlay which defines a single exterior pocket have been unsuccessful. Because they are monomers, polyolefin materials are not readily receptive to RF welding. The molecules within the thin sheets do not vibrate rapidly enough to generate enough heat to permit the polyolefin materials to plasticize and fuse. As previously stated, however, polyolefin materials are receptive to thermal welding. Thus, turned-edge casing boards made of thin sheets of polypropylene, for example, are able to realize the previously described advantages of thermal welding.
It is now apparent that a casing board used in the manufacture of articles for organizing, storing, protecting and displaying commemorative media is needed that includes a clear overlay which defines a transparent exterior pocket for displaying a single-sheet merchandising insert. Accordingly, it is the principle object of the invention to provide a casing board including a clear overlay which defines a transparent exterior pocket and a process for producing such a casing board. Although the preferred embodiments of the invention are described herein in connection with a casing board used in the manufacture of a loose-leaf binder and an audio cassette case, it is emphasized that the principles of the invention apply equally to casing boards used to manufacture similar articles such as portfolios, folders, notebooks, video cassette cases, compact disc holders, game boards and the like.